A TDMA mobile station transmits and receives data in blocks, with each block corresponding to a logical channel. A block of data is divided into four frames. Each frame is partitioned into eight intervals of time (slots). Of these eight time slots, some are allocated for the transmitting/receiving of a block element (a burst).
A mobile station transmits/receives packet data on packet channels, for example PDTCH (Packet Data Traffic Channel). Time slots are therefore set aside for the transmitting/receiving of packet data.
However, the mobile station is also likely to receive supplemental data during time slots not aligned with the allocated time slots provided for this purpose.
For example, the mobile station receives information concerning a neighbor cell, for example parameters for accessing this neighbor cell, a Location Area Code for the neighbor cell, etc. Such information allows, for example, connecting to the most favorable base station. This information is received on a logical control channel, for example the BCCH channel (Broadcast Control Channel).
There is also the data received on a paging channel, for example a PCH channel (Paging Channel).
When such additional data is received during time slots which overlap the time slots allocated for transmitting/receiving packet data, the mobile station stops transmitting/receiving the packet data for the entire duration of the packet data blocks corresponding to the overlapping slots.
Because of the non-alignment, a block of these additional data, for example a BCCH block, generally overlaps two packet data blocks, for example two PDTCH blocks. Therefore two packet data blocks may be lost when an unaligned block is received.
In addition, a BCCH time slot may cover two neighboring PDTCH allocated time slots corresponding to two respective PDTCH blocks. In this case four PDTCH blocks are lost for one block of additional data received.
Retransmission of these blocks is then required.